1. Field of the Invention
The present invention is generally directed to the field of semiconductor manufacturing, and, more particularly, to a method of controlling chemical mechanical polishing operations to control erosion of insulating materials.
2. Description of the Related Art
In modem integrated circuit devices, millions of transistors are formed above a surface of a semiconducting substrate. To perform their intended functions, these transistors, or groups of transistors, are electrically coupled together by many levels of conductive inter-connections, i.e., conductive metal lines and plugs. These conductive lines and plugs allow electrical signals to propagate throughout the integrated circuit device.
In general, these conductive interconnections are formed in layers of insulating material, e.g., silicon dioxide, HSQ, or other materials that may have a dielectric constant less than approximately 4. The insulating materials electrically isolate the various conductive interconnections and tend to reduce capacitive coupling between adjacent metal lines when the integrated circuit device is in operation. Moreover, modem integrated circuit devices are very densely packed, i.e., there is very little space between the semiconductor devices, as well as between the conductive metal lines. Accordingly, the amount of insulating material positioned between adjacent metal lines, and other surrounding conductive structures, both above and below the metal lines, is very important.
However, in the course of forming modem conductive lines and plugs, particularly out of copper, chemical mechanical polishing processes are used whereby the insulating material, e.g., silicon dioxide, between the conductive lines is lost or eroded away. Such erosion of the insulating material is undesirable due to its important function in modem integrated circuit devices.
The present invention is directed to a method that solves, or at least reduces, some or all of the aforementioned problems.
The present invention is directed to a method of controlling chemical mechanical polishing operations to control erosion of insulating materials. In one embodiment, the method comprises providing a wafer having a patterned layer of insulating material, a barrier metal layer, and a metal layer formed above the wafer, performing a first polishing operation on the wafer at a first polishing platen of the tool to remove a majority of the metal layer above the barrier metal layer, and performing an endpoint polishing operation on the wafer at a second polishing platen of the tool to remove at least some of the metal layer. The method further comprises performing a timed overpolish operation on the wafer at the second platen after the endpoint polishing operation is completed at the second platen, and performing a timed polishing operation on the wafer at a third polishing platen of the tool to remove substantially all of the barrier metal layer. The method concludes with the step of determining an erosion rate of the patterned layer of insulating material, providing the determined erosion rate to a controller that determines a duration of the timed overpolish operations to be performed on at least one subsequently processed wafer at the second platen, and performing the timed overpolish operation on the at least one subsequently processed wafer at the second platen for the duration determined by the controller.